This invention relates to an improved composition for water treatment in which polyvinyl alcohol is used in combination with a polyaluminum chloride as a flocculating and turbidity reducing agent.
It is known in the water treatment art to utilize polyaluminum salts such as polyaluminum chloride (PAC), polyaluminum sulfate (PAS) and polyaluminum chloride sulfate (PACS) as flocculating agents for the treatment of both potable and waste water. For example, U.S. Pat. No. 3,544,476 describes the use of a polyaluminum chloride as a coagulant.
Various methods are known for the production of these polyaluminum salts, which address problems of stability, seek to provide enhanced basicity or reduced sulfate, or strive to improve production yields or economics. As a general rule, however, each of these methods involves addition of a base to an aluminum salt solution to form hydroxylated aluminum species. Depending on the amount of base added, the initial product may be a polyaluminum salt or aluminum hydroxide. If aluminum hydroxide is formed first, the polyaluminum salt is then formed by the addition of additional aluminum salt to the aluminum hydroxide.
Regardless of the method of formation, these known polyaluminum salts are then added as flocculating agents to remove impurities from water. It is desirable to minimize the amount of material added, both from the standpoint of economics, i.e., minimizing the cost of water treatment, and from a health standpoint.
Accordingly, it is an object of the present invention to provide polyaluminum salt solutions which exhibit enhanced flocculating power such that lower concentrations of the polyaluminum salt can be employed.